MLA

Rand McNally and Company, Richfield Oil Corporation, United States. President (1817-1825 : Monroe). Monroe doctrine. Selections. U.S. defense map and Western Hemisphere strategic bases [cartographic material] : army camps, forts, flying fields, air bases, naval bases, mileage distances and flying times between important points, Panama Canal defenses, U.S. Navy patrol areas, propose. 1941?]. https://collections.library.yale.edu/catalog/15238309.

APA, 6th edition

Rand McNally and Company, & Richfield Oil Corporation, & United States. President (1817-1825 : Monroe). Monroe doctrine. Selections. (1941?])[U.S. defense map and Western Hemisphere strategic bases [cartographic material] : army camps, forts, flying fields, air bases, naval bases, mileage distances and flying times between important points, Panama Canal defenses, U.S. Navy patrol areas, propose]. https://collections.library.yale.edu/catalog/15238309.